Renal Lab Eval Flashcards
Kidney
- regulates what solutes
- secretes what hormones
- main 5 functions
solutes: sodium, potassium, hydrogen
Hormones: Renin, prostaglandins, bradykinin, EPO, calcium, phosphorus, and 1,25-dihydroxyvitamin D3 or calcitriol
5 Functions:
- regulate production of RBC
- regulates mineral levels
- regulate blood pressure
- regulate acid-base balance
- elimination of metabolic toxins and water through urine
What is Azotemia? Oliguria? Anuria?
Azotemia: elevated BUN and/or Creatinine
*the build up of abnormally large amounts of nitrogenous waste products in the blood.
Oliguria: decreased urine output
- U/O: less than 40oml/day
- U/O: less than 20cc/hr
- normal is 50-100cc/hr
Anuria:
U/O: less than 100ml/day
Differentiating azotemia: describe each..
- pre-renal failure
- intrinsic renal failure
- post renal obstruction
Pre-renal: volume contraction (may be dehydration, isnt actually renal failure)
Intrinsic renal failure: arteriolar damage (acute HTN), glomerulonephritis, Acute tubular necrosis (kidney parenchyma is damaged)
Post renal obstruction: ureteral obstruction, bladder outlet obstruction (kidney parenchyma is okay but there is some type of obstruction, the waste product is filtered just cant be emptied)
GFR
- whats normal for men and women?
- influenced by
- can be measure by
Normal:
- men: 130ml/mn
- women: 120ml/min
Influenced by: age, sex, body size, race
Can be measured by: creatinine clearance, urea clearance, inulin clearance (*gold standard for GFR)
In patients with kidney dz, reduction in GFR……
- either progression in underlying kidney dz or superimposed reversible problem, T/F?
- level of GFR has prognostic indications but is NOT an exact correlate to the loss of nephron mass, T/F?
- stable GFR does not necessarily imply stable dz, T/f?
- some patients w/ renal dz may go unrecognized b/c they have normal GFR, T/F?
they are all TRUE.
BUN
-comes from what?
- when might it be increased? decreased?
- normal range
Urea nitrogen is what is formed when protein breaks down
*when protein is used for energy the carbon is cleaved and nitrogen is left behind and then forms ammonia. Ammonia is processed through the liver to become urea, when urea enters blood stream its called blood urea nitrogen which is then excreted by the kidney.
Increased:
-Renal Dz (failure) **
- excessive protein breakdown
- very high protein diet
- GI bleeding
Decreased:
-liver dz (if liver is unable to convert ammonia to urea then the BUN will decrease and ammonia increases)
-starvation
Normal: 6-20mg/dl
Creatinine Clearance:
- normal values for men and women
- use?
Normal:
-Men: 107-139ml/min
-women: 87-107ml/min
Used to assess GFR
Decreased GFR can lead to increased bun in 2 ways…what are they
- decreased flow through the glomerulus
2. slower transport time allows more BUN to be resorbed at the level of the Proximal Convoluted Tubule
Where does creatinine come from ?
what is normal creatinine for men and women?
50% loss of renal function is needed to increase serum creatine from 1.0 to ___?
creatinine is formed from the normal breakdown of muscle.
Men: 0.8-1.4 mg/dL
Women: 0.6-1.2 mg/dL
2.0mg/dL so, this means creatinine has a very narrow range.
When might creatinine be increased? Decreased?
Increased:
-renal failure
- diet (increased ingestion of meat)
- Meds: ACEi, diuretics, NSAIDS
- Muscle Dz: muscular dystrophy, rhabdo
Decreased:
-pregnancy (normal, 0.4-0.6mg/dL)
BUN Creatinine Ratio
- normal
- elevated
- what causes BUN to be disproportionately increased?
- what causes the BUN/Creat ratio to go up proportionally?
Normal: 10-20:1
Elevated Greater than 20:1
- BUN is disproportionately increased when azotemia is d/t pre-renal causes (such as dehydration)
- if renal dz the BUN/Creat ration should go up proportionally. (this would be intrinisic dz)
What are some examples of Increased (greater than 20:1) BUN w/ normal creatinine?
What are some causes of increased (greater than 20:1) BUN w/ proportionately increased creatinine?
elevated BUN:
- pre-renal dz
- catabolic state w/ increased tissue breakdown
- GI hemorrhage
- High protein intake
- drugs like tetracycline and steroids.
Elevated BUN & Creat:
- Post-renal dz (obstructive uropathy)
- pre-renal dz superimposed on renal dz(intrinsic-renal dz)
What are some examples of decreased ratio (less than 10:1) w/ decreased BUN?
What are some examples of decreased ration (less than 10:1) w/ increased creatinine
Decreased ratio and decreased BUN :
- acute tubular necrosis
- low protein diet, starvation, sever liver dz
- repeated dialysis
- SIADH
- pregnancy
Decreased ratio and increased creatinine:
- rhabdo
- muscular pts who develop renal failure
Regulation of K+
- how do we gain it
- how do we lose it?
- why is it important to be efficient at regulating K+?
- we eat it…50-100mEq daily
- kidneys are main source of K+ loss, 80-90% lost in urine, remainder lost in stool or sweat
- because K+ is all contained within our cells with an exception of 2% in ECF…a small change (1-2%) can lead to dangerously high serum levels!
K+ homeostais is dependent upon…
- pH
- renal function including effects of diuretics, aldosterone, and renal parenchyma
- GI fluid losses